In-flight entertainment (IFE) systems have been deployed onboard aircraft to provide entertainment for passengers. The in-flight entertainment systems typically provide passengers with electronic content, such as movies, television, and audio entertainment programming IFE systems are increasingly using wireless access points to stream electronic content from a content server to passenger terminals, seatback video display units, and other communication terminals within the aircraft. In view of the large number of simultaneous high-bandwidth communication sessions that can be required to support video streaming within an aircraft fuselage, the wireless access points can have high-power transceivers connected to directional beamforming multiple-input multiple-output (MIMO) antennas.
Mounting MIMO antennas within an aircraft fuselage is complicated by requirements for maximizing space available for passengers and balancing the need for reserving space for flight critical systems, crew systems, passenger facilities, etc. Moreover, identifying locations for MIMO antenna mounting is further complicated by the need to balance antenna coverage with reducing interference to other MIMO antennas and flight critical systems. Consequently, MIMO antennas are increasingly being integrated into passenger seating areas, fuselage interior sidewalls, bulkheads, overhead storage panels, and other locations where passengers can be located.
It is therefore becoming increasingly likely that passengers can fall asleep against, lean against, stand next to, or otherwise be very close to these antennas. The presence of a passenger's head, hand, or other body part against one of the MIMO antennas can cause radiation pattern distortion or detuning of the antenna and absorption of the radiation, thus affecting the efficiency and correlation performance of the antenna. Moreover, the antennas can have deleterious effects on passengers' health. The World Health Organization (WHO) has classified the radiation generated by radio frequency (RF) transmitters as possibly carcinogenic. Other health concerns from such radiation can include triggering a passenger's electromagnetic hypersensitivity, cause thermal or heating effects to a passenger, cause loss of memory or other deleterious cognitive effects, and interfere with operation of a passenger's electro-medical device such as a pacemaker or hearing aid.